1. Field of the Invention
The present invention is directed in general to integrated circuit devices and methods for manufacturing same. In one aspect, the present invention relates to the manufacture and use of field effect transistor devices.
2. Description of the Related Art
Semiconductor devices used in high-efficiency power amplifier (HEA) applications require higher speed and power handling capability. To meet these operating requirements, high power semiconductor devices may be formed with semiconductor materials, such as gallium nitride (GaN), having material properties that are suitable for use in such applications. For example, high speed transistor switch devices, such as high electron mobility transistor (HEMT) devices, formed with GaN-based materials offer many advantages in RF applications, especially in HEA applications, by delivering high current, high breakdown voltage, and high unity gate current cutoff frequency (fT). However, as the speed of the devices is increased by shrinking the gate length and increasing the electron concentration in the device channel, gate and drain leakage currents can increase and device breakdown voltage can be reduced. Attempts to reduce gate leakage current in such devices may adversely affect other device properties. For example, device features and processing steps used to reduce leakage current can degrade the fT of the device by adding gate capacitance. In addition, the gate electrode device features at the edges of deep submicron gates can create electric fields which destabilize the wafer surface, impair the breakdown voltage, or otherwise produce surface damage that induces interface traps causing RF current collapse.
It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for purposes of promoting and improving clarity and understanding. Further, where considered appropriate, reference numerals have been repeated among the drawings to represent corresponding or analogous elements.